When going with a bigger MAF you should also lower your minimum maf voltage setpoint because you will be closer to it with a larger maf at idle. It could possibly set off codes.

Another trick is to put a honeycomb air straightener out of a GM maf in your sample tube. The honeycomb out of a 3" GM maf will press fit directly into a ford 70mm sample tube. It will dramaticly clean up your maf's voltage signal and makes your MAF respond the same way regardless of positioning near bends.

MAfs are designed to meter Mass Air flow when the air is at or near standard pressure and density. When you put your MAF in a blow through configuration after the turbocharger you are trying to make it meter air in a way it is not designed to. It is much harder to tune in that configuration because of the dynamics of the environment. I always make mine draw through. It works much better for me.

Keep in mind it is only truly nessecary to upgrade your MAF when when you have reached the limit of its metering capability(4.5+ volts). If your routinely getting way up there then you should consider upgrading MAfs. I dont think the stock Zetecs will max out thier stock MAF but if your going turbo you will need at least a 70mm.

1. Force the EEC to run in open loop. This makes it much easier to tune the lower voltage part of the function because the o2 sensor is not having any say over fuel.

Why, when the trims tell you exactly where you need to be?

Quote:

Originally Posted by ford_boy

MAfs are designed to meter Mass Air flow when the air is at or near standard pressure and density. When you put your MAF in a blow through configuration after the turbocharger you are trying to make it meter air in a way it is not designed to.

If you read the wiki article I linked you will understand that it IS designed to do that.

If any of you are wondering the proper way to tune your MAF transfer table. There are a few steps you should follow to make th process much easier.

1. Force the EEC to run in open loop. This makes it much easier to tune the lower voltage part of the function because the o2 sensor is not having any say over fuel.

2. Set your base fuel table to 12:1. This is your target AFR.

3. Datalog. You will need to log AFR with a wideband and you will need to log MAF voltage. TPS and RPM are fun to have but are not needed. Make sure your engine is heated up all the way before logging cause cold start enrichment will throw it off a little.

First you log the 0-2 volt part of the curve. Once the car is running and heated up and you start logging. leave it in neutral. Ease on the throttle slowly and steadily. keep increasing the throttle until you reach 2 volts or you dont want to free rev it any higher.

Once you are done the log. Then you need to tune. for example. if at 1.2 volts your afr is 14:1 and your target afr is 12:1 then you need to multiply the airflow value at 1.2 volts by 1.16. You go through all of the values from 0v to 2v in the same manner. The process may have to be repeated a few times to get it as close as possible.

Then you are ready to do some datalogs while driving for the 2v to 5v section of the transfer. You always want to ensure that you are starting in the rich side. Doing hard pulls leaner than 12:1 can get dangerous. Especially with forced induction. I find a good way to get a ballpark figure of what the transfer values should be before starting is multiply the values proportionaly to the size of the MAF upgrade.

For example. If your starting with a 60mm maf and converting to an 80mm maf then you would multiply all the values by 1.3 as a starting point.

Again, you get the engine up to operating temp. Then you find a nice open strech of road ( or a dyno). You get logging and start doing moderate pulls. I find 3rd gear works real well. You want to make sure to make slow and steady pedal movements. This helps to make nice smooth datalogs that are easy to read. Let the car slow down to the bottom slowly accelerate to the top of the gear. If you are on the rich side then it is ok to start doing some good hard pulls as long as it stays on or below 12:1afr.

Once you think you have enough clean data to tune as many data points on the curve as you can (except the high 4v area. If you get up here you still need a bigger MAF!). Then you start rebuilding your curve by multiplying the airflow values at each voltage data point relative to the amount that the logged AFR is away from your target 12:1afr. You may have to repeat this process a few times to get it perfect.

When the MAF transfer is spot on. The AFR will hold at 12:1 all the time. Idle, light cruise and WOT. The only time it should stray fronm 12:1 is when decelerating.

Once you have the MAF curve done. Then you are free to set Base Fuel table back to stock and enable closed loop fuel control. That way you can have you lean idle and cruise with input from the o2 sensor.

PLEASE ! ! People DO NOT tune your car like this , there is SOOOOO much wrong info in here I dont even know where to start

I view closed loop operation as a variable, and opt to disable it. You use it to your advantage.

Perhaps you didn't notice the end

Quote:

When the MAF transfer is spot on. The AFR will hold at 12:1 all the time. Idle, light cruise and WOT. The only time it should stray fronm 12:1 is when decelerating.

Once you have the MAF curve done. Then you are free to set Base Fuel table back to stock and enable closed loop fuel control. That way you can have you lean idle and cruise with input from the o2 sensor.

Tom, It seems to me, both our stratagies have the same end result.
I agree, your way does sound easier.

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